Networks, such as using Dense Wave Division Multiplexing (DWDM), Optical Transport Network (OTN), Ethernet, Multiprotocol Label Switching (MPLS), and the like, are deploying control plane systems and methods. Control planes provide an automatic allocation of network resources in an end-to-end manner. Exemplary control planes may include Automatically Switched Optical Network (ASON) as defined in ITU-T G.8080/Y.1304, Architecture for the automatically switched optical network (ASON) (February 2012), the contents of which are herein incorporated by reference; Generalized Multi-Protocol Label Switching (GMPLS) Architecture as defined in IETF Request for Comments (RFC): 3945 (October 2004) and the like, the contents of which are herein incorporated by reference; Optical Signaling and Routing Protocol (OSRP) from Ciena Corporation which is an optical signaling and routing protocol similar to Private Network-to-Network Interface (PNNI) and Multi-Protocol Label Switching (MPLS); or any other type control plane for controlling network elements at multiple layers, and establishing connections among nodes. Control planes are configured to establish end-to-end signaled connections such as Subnetwork Connections (SNCs) in ASON or OSRP and Label Switched Paths (LSPs) in GMPLS and MPLS. Note, as described herein, SNCs and LSPs can generally be referred to as services or calls in the control plane. Control planes use the available paths to route the services and program the underlying hardware accordingly.
In addition to control planes which are distributed, a centralized method of control exists with Software Defined Networking (SDN) which utilizes a centralized controller. SDN is an emerging framework which includes a centralized control plane decoupled from the data plane. SDN provides the management of network services through abstraction of lower-level functionality. This is done by decoupling the system that makes decisions about where traffic is sent (the control plane) from the underlying systems that forward traffic to the selected destination (the data plane). Examples of SDN include OpenFlow (www.opennetworking.org/sdn-resources/onf-specifications/openflow/), General Switch Management Protocol (GSMP) defined in RFC 3294 (June 2002), and Forwarding and Control Element Separation (ForCES) defined in RFC 5810 (March 2010), the contents of all are incorporated by reference herein. Note, distributed control planes can be used in conjunction with centralized controllers in a hybrid deployment.
Restoration (also referred to as protection) is a key feature in networks where a backup (protection) path takes over for an active (working) path of a service or call when there is a failure in the active path. Restoration can include dedicated, reserved protection paths (e.g., 1+1) for working paths which provide extremely fast restoration (sub-50 ms) at the expense of inefficient bandwidth usage, i.e., the protection paths are active and unused in the network. At the other end of restoration time is mesh restoration which includes computing paths at the time of failures and can lead to several seconds for restoration. Of course, unprotected services can be provisioned without restoration capabilities. Various techniques are used in between these extremes (dedicated protection and mesh restoration with path computation upon failures) to balance the inefficient use of bandwidth versus restoration time. Of course, in terms of restoration, the goal is to minimize restoration time while concurrently minimizing the inefficient use of bandwidth. It would be advantageous to support dedicated protection paths which provide the advantage of quick restoration time, without the disadvantage of inefficient bandwidth usage.
MPLS offers backup path capabilities via Fast Reroute (FRR), but these backup paths, when established in the network, are established at the same priority as the active path. Thus, network operators in MPLS must be careful not to exhaust all of the free network bandwidth for backup paths to leave some bandwidth available for dynamic reroutes (mesh restoration). In mesh restoration, such as for control planes like ASON, GMPLS, and OSRP, leading techniques include pre-calculation of mesh restoration paths, without establishing these paths. Note, mesh networks are typically engineered to have some spare bandwidth available for use when failures occur, but this is less than previous ring-based techniques which had dedicated spare bandwidth (e.g., 50% of the bandwidth). Pre-calculation saves only a small amount of restoration time because the overall traffic recovery time is governed by the time it takes to signal and establish a new path in the network, i.e., path computation time is only a small fraction of the overall connection establishment time. That is, pre-calculated routes in mesh restoration save a little time. Again, it would be advantageous to have the restoration time of already established backup paths while not stranding this bandwidth for use in the network.
In networks with control planes, SDN, etc., connections can be assigned priority levels which are used for preemption in restoration, service creation, and the like. In particular, the connections can be Layer 0 (wavelengths), Layer 1 (Time Division Multiplexed (TDM), Layer 2 (Ethernet, MPLS, etc.), or a combination thereof. For example, in digitally multiplexed optical networks, connection priorities can be configured during creation and these priorities are static for the life of the connection. High priority connections can be restored immediately such as through mesh restoration whereas low priority connections can be restored after a hold off period or the like to enable the high priority connections an opportunity to obtain resources first. This conventional approach leads to non-intelligent behavior, i.e., current information is not utilized to make intelligent decisions about what should be restored immediately or delayed. For example, if may make sense to delay a high priority connection to allow many additional needier connections an opportunity. Various other situations are also seen. That is, it is inefficient to make decisions at run time based on previously configured static priorities.
Disadvantages of this static priority approach include the following. For static high priority connections, when such connections' paths are path protected, restoration would already be done by this path protection rather than mesh restoration, thus it does not make sense to mesh restore such as connection since other needier connections' could get delayed. Static high priority first restoration is always a “greedy” connection approach which is not optimal from network performance perspective, since ideally only connections should mesh restore first which would result in traffic restoration. For static low priority connections, often path protected connections (which may be high priority) are set to low priority due to the additional path protection. However, when path protection is not available (e.g., because of fault in other leg not restored), mesh restoration is low priority (delayed restoration) resulting in high traffic restoration times. This approach is always “courteous” to other connection in network, which is not optimal for connection itself when restoration would result in traffic restoration (because of protection not being available).